Following reports of norovirus-like illnesses in people who report eating raw oysters from several areas in Washington and elsewhere, public health officials at the Washington State Department of Health have tracked down commercial shellfish harvested areas where some of the illness-linked oysters were harvested.

Over the past several weeks, small harvest closures and recalls have been ordered, the largest of which is in Hammersley Inlet in Mason County, where a recall has been issued for any shellfish harvested there since March 15. Smaller portions of the shellfish harvesting area were closed and shellfish recalled on March 2, April 4 and April 5.

The three-mile stretch of commercial shellfish growing beds is about two-thirds of the Hammersley Inlet growing area and is harvested by 31 shellfish companies. Shellfish harvested from the area is typically shipped to many states and countries. Shellfish growers and the Department of Health are working with local health jurisdictions and other states to track down all harvested product to make sure it is not available to be consumed.

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“We are actively evaluating all potential pollution sources in the area to determine what is causing the contamination. The area will remain closed until we can assure that public health is protected,” said Rick Porso, Director of the Office of Environmental Health and Safety. “This issue underscores the importance of protecting our marine water, especially in areas where shellfish are grown.”

Norovirus is a common stomach virus that spreads easily. It can be transmitted through contaminated food or surfaces and person-to-person contact. The source of norovirus is people — specifically, the feces and vomit of infected individuals. The virus can be present in marine water indirectly through boat discharges, failing septic systems, malfunctioning wastewater treatment plants, or directly from an infected person. Because shellfish are filter feeders, they can concentrate the virus and infect people who eat them raw or undercooked.

Norovirus symptoms include watery diarrhea, vomiting and stomach pain. Most people get better within two days. Dehydration can be a problem among some people, especially the very young, the elderly, and people with other illnesses. For those consumers concerned about the increased risk of illness, ordering and eating cooked shellfish is an effective way to prevent norovirus illness.

The Department of Health is responsible for the safety of commercial shellfish harvested in the state. The agency’s Office of Environmental Health and Safety uses national standards to classify all commercial shellfish harvesting areas. People who gather their own shellfish should always check the Shellfish Safety Map to learn about closures or health warnings.

Commercial Growing Area Classifications

Approved – When the sanitary survey shows that the area is not subject to contamination that presents an actual or potential public health hazard. An Approved classification authorizes commercial shellfish harvest for direct marketing.

Conditionally Approved – When it meets Approved criteria some of the time, but does not during predictable periods. During these periods the area is closed. The length of closure is predetermined for each Conditionally Approved area, and is based on water sample data that show the amount of time it takes for water quality to recover and again meet Approved criteria. Once that time period has elapsed, the area is reopened. Here are two examples of when a Conditionally Approved area would be closed to harvest:

During dry weather an area may meet Approved water quality standards, but after a certain amount of rain falls (termed a “rainfall event”) the water quality declines. The area is temporarily closed to harvest after a rainfall event.

Some bays are rarely used by boaters in the winter but experience high boater use in the summer. Under these circumstances the bay is open for harvest during the winter and closed during the boating season.

Restricted – Water quality meets standards for an Approved classification, but the sanitary survey indicates a limited degree of pollution from non-human sources. Shellfish harvested from Restricted growing areas cannot be marketed directly. They must be relayed (transplanted) to Approved growing areas for a specified amount of time, allowing shellfish to naturally cleanse themselves of contaminants before they are harvested for market.

Prohibited – when the sanitary survey indicates that fecal material, pathogenic microorganisms, or poisonous or harmful substances may be present in concentrations that pose a health risk to shellfish consumers. Growing areas adjacent to sewage treatment plant outfalls, marinas, and other persistent or unpredictable pollution sources are classified as Prohibited. Commercial shellfish harvests are not allowed from Prohibited areas.

Recreational Beach Classifications

Open – The beach meets health standards and the area is safe to harvest.

Conditionally Open – The beach meets health standards and the area is safe to harvest; however, certain conditions can cause an unsafe harvest and the beach will be closed. The beach may also contain multiple classifications. Excessive rainfall, boating, and certain seasons may result in permanent or temporary beach closures.

Closed – The beach does not meet health standards and is closed. Shellfish are not safe to eat.

Unclassified – Health standards have not been evaluated for this beach. Shellfish harvesting is not recommended.

Open classifications don’t always mean you can harvest. The Department of Fish and Wildlife sets limits and harvest seasons to prevent overharvesting. Check Fish and Wildlife’s website to make sure you can legally harvest there.